


A Certain Indescribable

by Luna_Sin_Sin



Category: Swapfell - Fandom, Underfell - Fandom, Undertale
Genre: Angst, Bonezone Compilation, Concent, Fellcest - Freeform, Fluff, Fontcest, Inspiration Driven, Kinks, M/M, Multi, Mythtale, Mythtale Au, Porn With Plot, Porn with Plots, Shagfrick, Smutt, Swapcest - Freeform, Swapfell, Talecest, Underfell, Underfell Sanster, Undertail, non-con, swapfellcest - Freeform, underfrick, undershag
Language: English
Status: In-Progress
Published: 2017-01-17
Updated: 2017-10-31
Packaged: 2018-09-18 03:56:40
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings, Rape/Non-Con
Chapters: 5
Words: 12,611
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/9366959
Author URL: https://archiveofourown.org/users/Luna_Sin_Sin/pseuds/Luna_Sin_Sin
Summary: A collection of stories that center around Fellcest & Swapfellcest (with Talecest & Swapcest on the way if the want is there). The majority are one-shots with some plot, while others are inspired by artworks I wrote fanfiction for. I also like to throw in some personal headcanons for the characters and universes I write.





	1. Underfell; Waxing Bones & Choked Moans

**Summary for the Chapter:**

> Papyrus is bedridden from a healing injury, but when Sans makes one too many puns - or several - Papyrus shows him just because he can't fuck him, doesn't mean he can't fuck him. He also discovers Sans had a kink he wasn't aware of... In fact, he finds he has the same one.

**Notes for the Chapter:**

> Hello everyone! I'm writing these sort of for fun, as an early birthday present to me. Since these are for fun and based on writing inspiration like kink and prompt generators, most of these will always contain smut not all will be sin from start to finish. It all depends on my imagination, and feedback from you guys.
> 
>  
> 
> UPDATE: This chapter has been rewritten.

 

 

            Unacceptable.

            Completely unacceptable. This sort of thing just couldn’t happen to him. He was The Great and Terrible Papyrus. When he strode through town monsters moved to get out of his way. The rowdy dogs in the Royal Guard, who only quaked and totally behaved for Captain Undyne, heeled at his command.

            In battle, he was superior to all but Undyne and King Asgore himself. He could take on numerous enemies at once and still come out victorious, even flawlessly triumphant!

            He was feared, revered, and surely… popular!

            Well, he did have popularity, just not in a positive image. But no matter. Being feared – being revered – it was far better than his old dream of being lavished with love for his personality. He had Sans for that now, anyway. In fact, he’d take Sans’ version of _worship_ over the common monsters anyway.

            Thinking of Sans made him grit his teeth and dig his fingers into his arms. He eyed the covers balefully, where underneath, his hip and femur were wrapped in bandages. The injury needed a few days’ rest if he wanted it to heal stronger, but this anxious wait was…

            It was heavy.

            He was in this mess because of that blasted Dr. Alphys. Undyne had been called away to the Capital and she’d left him temporarily in charge of the Hotlands. She’d made it none-too-subtle with the punch to his shoulder that when she wanted him to patrol around the labs SEVEN times, he was to do so without questions.

            Really, he had no idea what Undyne saw in that nervous, fumbling, scientist woman, but an order was an order… Besides, Undyne had trusted him with her weakness instead of anyone else. Much like how she was aware of his relationship with Sans, he’d quickly caught ahold of hers… With Sans’ rather careless and unexpected announcement, at that.

            “ _What?”_

_“Hm? Yeah, the Captain and the Royal Scientist. They’re in cahoots.”_

_“…you mean, staging a coup?”_

_“What, no? Not that I know anyway. I just mean they’re like, y’know, us. Fucking the rats out of the walls an’ all.”_

_He’d said it so casually, sucking on his mustard as he’d gone to drop some dead leaves on his pet rock._

_“How do you possibly know such a thing?”_

_Sans had glanced back at him, confusion evident._

_“Isn’t it obvious…? Everyone knows that, right?”_

_Everyone certainly did not know that. Papyrus refused to believe he could be the only one who hadn’t noticed it… There were certainly signs now that he was looking for them, but not enough to think… Undyne even spoke about Dr. Alphys impersonally… Flippantly, and always by title._

_Something had changed on Sans’ expression then, something that sounded peculiarly like fear edging its’ way into his voice._

_“…right?”_

So, knowing their relationship, he’d done the rounds and respected Undyne’s wishes. And who would have thought, on one of those rounds by the labs he’d heard explosions going off. No sooner had he run in and approached the scene, he’d seen Dr. Alphys knocked to the floor by some sort of robot prototype that had looked suspiciously like Mettaton approaching her with a ticking timer.

            Getting her slow and awkward body off the floor and out from the malfunctioning machines exploding throughout the lab was how he’d gotten injured. A blast caught him off guard as he sheltered the weak scientist from the flying blasts of electricity and the explosion itself.

            Only outside the labs had he realized how badly he’d taken damage to his femur and hip, but had resolutely done his best to ignore it until he’d tried to turn away to give Undyne her moment with the doctor. Only then had the pain become apparent, as well as the injury itself.

            The only good thing to come from the whole mess in his opinion was that Undyne had sworn that no one would get the jump on him while he was resting in bed, she’d make certain of it – and now, Undyne, Captain of The Royal Guard – owed him one.

            That still left a smirk on his face to think about. Sans too, had seen the advantage of the whole situation… after he’d stopped panicking seeing him half-collapse to the couch to rest when he got back home.

            But his brother’s distressed expression kept appearing in his mind, his panic laced voice and the nervous energy he hadn’t shaken off until he’d personally seen Papyrus get into bed and rest. Not that something so simple caused it to go away, no, it had taken two days to get his brother to shake off the pesky habit of annoying him every five minutes.

            No matter how many times he had explained to Sans that bones healed stronger after they broke if you allowed them to rest on their own for a while first – a theory tested and proven numerous times thanks to Undyne’s… enthusiasm and lack of finesse in the old days – his brother had refused to let up on the matter of healing until this morning, where he’d simply been morose all day long.

            Probably just to spite him.

            For someone so willingly submissive in the bedroom, Sans had a stubborn streak in his personality that even Undyne would have trouble throwing a spear at.

            But again, thinking of Sans made him clench his jaw and beyond frustrated. His brother needed him to be up and moving – how Papyrus preferred it – but not just because seeing him laid up made him so stir-crazy and pestering, but because people _feared_ him.

            …Sans, not so much.

            As much as it irked him, Sans had already made a reputation in Snowdin before the two of them had… reunited after their parting years prior. It was almost common knowledge his brother only had one HP, and he could still remember people scoffing and asking him twice if he was really Sans’ brother, his _younger_ brother.

            If their enemies found out that he was laid up like this… If they attacked the house or Asgore forbid, strike out against his brother…

            Unacceptable.

            He just needed one more morning. Then, he’d get healed up and his cracked femur and hip would be stronger than before. _He’d_ be stronger than before.

            _Sans, get back now._

Although he hadn’t wanted Sans to go out on his own and Sans hadn’t been crazy about leaving him by himself, they’d both agreed that as long as the town saw one of them doing their job around town appearances could be kept up. His brother had stopped by frequently enough during breaks – and what he was certain were _not_ breaks – to keep him updated regularly on things.

            But he’d gone to that hole in the wall establishment called Chillby’s for food. He hated not being able to classify one thing as a threat or not, but Chillby himself was definitely both an asset and a threat. An asset because he knew that from Sans’ prior ‘relationship’ with the bartender, they had a very… personal history together, and both counted each other as allies. Chillby would never allow anyone to dust Sans in his establishment. That much, Papyrus knew for certain.

            But the threat was _because_ of Sans and the bartender’s past together. Without a doubt, Chillby still wanted to fuck his brother. He’d had words with the bartender, clear and under-no-means-not-a-threat-talk words with the monster and what he’d do to him if he touched his brother.

            That talk had been unsavory as one would imagine.

            Truthfully, for as much control as Papyrus had, he didn’t trust himself to stop by Chillby’s often. If he saw Chillby try to touch Sans just to antagonize him like he had after their ‘talk,’ he’d probably kill him then and there. Which would mean he’d be kicked out of the Royal Guard.

            …and Sans would likely be pissed off as well. There was that too.

            A familiar pop filled the air, not so much sound-wise but a pop in pressure. He’d become accustomed to the signs of Sans teleporting – an ability that still boggled his mind and made him secretly envious – and turned to look at the doorway expectantly as not too long afterward, he heard his brother walk up the stairs. He still wondered why Sans didn’t just appear in the room he wanted to be in, but whenever he asked Sans would only shrug with an odd expression.

            It truly was like his brother to be gifted something as cool as teleportation, and yet somehow make an already lazy-like power even lazier.

            He pushed himself to his elbows to move toward the headboard as Sans came in, balancing two take-out boxes of monster food on a tray lit by some cheap blood red candle. If it was Sans’ way of romanticizing food that he hated for him, it was a lot like Sans himself: lazy.

            “Heh, don’t get up on my account.”

            His brother strolled in and plopped himself down beside him on the bed, an easy-grin on his face as he sat the food down on the end table. A new and annoying game that his brother was playing with him was a game of fasting. As far as he could tell, Sans was refusing to eat until he did. But before he could open his mouth to say another rebuke and start up their earlier argument, Sans slid his hand over the blanket to rest it on his injured femur. He’d been subconsciously doing that nearly every chance he got. Papyrus couldn’t tell the reason behind it, except that perhaps in his brother’s mind, he was… checking to make sure the limb was still there?

            His brother was hard to read at times.

            “You sure took your time at that backward tavern.”

            “Come on now, the best thing to do was act natural, eh? So I did what I always do. What's that word you often use? Ah, yeah, I boondoggled.”

            “If there is anything you do well, it is that brother.”

            “Ah shucks, you’ll make me blush bro.”

            Getting up, he headed for the bookshelf to scan the books there. He could tell Sans planned to read to him, perhaps because he was injured? Try as he might to resist it, when he saw Sans select Peek-A-Boo with Fuzzy Bunny his mood lightened. It was a child’s book – a book loved by a different, much younger and far more idiotic Papyrus…

            Truly, he wasn’t a sentimental person… The only item he valued with a personal attachment was his scarf, and it was mainly just because it was versatile and added a flare of danger to his appearance… Certainly not because it was a present from Sans, and not because he liked the color.

            “You know, Papyrus… It’s been so long since we read Peek-A-Boo with Fuzzy Bunny that these days, he’s just some bunny that we used to know.”

            “Sans.”

            By Asgore’s Trident, he hated puns. As some sort of petty revenge for refusing to heal right away, he was certain his brother had been plaguing him with puns intentionally. The amount of bomb and electrical puns that he had been forced to endure already had made him throw Sans bodily from the room just earlier today.

            “Watt, I’m am I not very bunny?”

            He was fifty-percent sure that was another electrical pun alongside another rabbit one.

            “If all you plan to do is pun your way through this conversation, see yourself out. I’m in no mood.”

            “Fine, fine, I guess I’ll just have to hop to it.”

            He could only growl in annoyance as Sans sat down beside him legs again, resting against his femur as he held the book up and flipped idly through the pages.

            “Where do you wanna start, bro? Beginning? Somewhere in the forest…? How about at the Great Crack?”

            “Sans I swear to god that I will break you.”

            “…hm, technically that was a pun on your part too.”

            “Sans…”

            “Eh, you can break me anywhere. Here, take a piece.”

            With revulsion, he watched Sans take his hand off from his wrist. He still didn’t know how his brother managed to do that – to take off his bones like it was nothing, and place them back into place so easily. It still baffled as much as witnessing it the first time had. When he had tried to do it himself right afterwards, not only could he not get the bones to detach, but it had hurt. Sans still refused to tell him the secret, and Papyrus refused to give up on the puzzle and demand the answer.

            Of course now of all times Sans would gloat in this way.

            “Put that back on at once.”

            “Hehehe, sure thing bro. This trick isn’t as handy as one might think.”

            _Bare it,_ he chanted, _bare it. He just wants to make you angry._

“I guess them are just the breaks... Tibia honest, I can't believe you got shocked by this old trick of the hand again. How are you currently feeling?”

            “One more pun… I dare you.”

            Perhaps that was not the best thing to say to someone who very obviously had a desire to flirt with his temper, knowing he had immunity from being dusted unlike anyone else did.

            “Hehe, oh c’mon, bro… I’m just amped up to see you and all.”

            He seized his brother by the back of the skull and shoved him face first into the sheet. He would suffocate him before he told his next pun, he swore it!

            “That was at least your thirteenth pun today, Sans. You really are trying to anger me intentionally, aren’t you? Did you think because it is hard for me to get out of this bed that I couldn’t retaliate?”

            “Ack, Paps, your leg…!”

            “Silence. Actions have consequences. I shall see you punished, brother.”

            The _how_ was the question. Sure, he could do something as simple as take away his mustard privileges, but he wanted a more immediate discipline... His eye caught the flash of the candle flame on his end table, and the oozing wax sliding down its body.

            Perfect.

            He was sure Sans would appreciate the irony of bringing his own punishment down on himself, in more ways than one. Sans didn’t seem to like the look that stole over his face.

            “Boss…?”

            Reaching out, he yanked Sans’ sweater up past his ribs before seizing the candle and dragging it to hover over Sans’ spine. His brother could tell he was doing something, but couldn’t see what. The hot wax singed his fingerbones as he let it pool above, a burning stab he was sure would make his brother _writher_.

            The few drops took a second to register, but then Sans bucked only for him to shove his face back down into the mattress. His voice was muffled through the sheet.

            “Hot, nngh, ah! Shit!”

            “Nyehehe, not so punny now are you?”

            To his own horror, he realized he’d just said a pun without meaning too. Sans struggled to turn his head to look at him through his fingers, something vindictive in his squinting gaze.

            “Welp, you could say we really waxed ourselves into this position, couldn’t you?”

            _That’s it!_

Absolutely furious, he moved his hand to the front of Sans’ throat, squeezing tightly as he brought the candle to spill over Sans’ middle and lower spine. He tilted the hot wax onto his bones, watching it pool down each curve and collect onto others. Seeing the red wax drip and stain his convulsing brother made it look like he was injured, and somehow, his Sans seemed more erotic than before. Especially with the way he gasped and clung to the hand strangling him.

            If Papyrus was sure of anything, it was that Sans made the most stimulating sounds imaginable, even when he was being strangled. Deep, raspy, needy noises, even when he was in pain – especially when he was in pain.

            Yes, he was certain there was no better pleasure than witnessing his brother like this. The sounds he made, the way he struggled _just_ hard enough to look committed to the part, and especially the haze that took over his gaze when he was really feeling it. The only thing better was how he felt inside during all this.

            Which brought up to serious concerns. One being that if he fucked Sans, he couldn’t really call this a punishment… And two, he couldn’t really thrust in his condition without hurting himself. It was an evenly frustrating situation, considering how much he wanted to take Sans here and now.

            A hand moved to his femur and rubbed the area, squeezing it tightly, and he felt a peculiar jolt travel through Sans that didn’t match the wax falling onto his brother’s bones. A slow but sudden epiphany came over him then as his eyes traveled down Sans’ frame and the wax wounds clinging to him.

            “You randy little shit…”

            He released Sans’ throat, having been mentally counting the minutes in his head so he didn’t cause Sans to suffocate into unconsciousness, and watched as he clutched his throat and gasped.

            “Haah, haah, ah, haah, ahahaha… you could… say I’m in a breath…less situation.”

             Seizing Sans by the ribs and forcing him to turn and look at him on trembling knees, he growled, “Enough! You really are antagonizing me purposefully, aren’t you? Are you doing it just to rile me up because I haven’t healed yet, or because you want to be fucked? Because if it’s the former I will leave you dry for a full week as punishment.”

             Sans panted, groaning and shifting back on his hands as his knees trembled from being lifted by Papyrus' grip. When he remained silent except for his wheezing, Papyrus released his ribs and let Sans collapse backward onto his hands. Despite having to have been dizzy, Sans kept himself lifted to keep his weight off Papyrus' leg. Though he moved his hand back onto Papyrus' injured femur right after, but unlike Papyrus had predicted, Sans didn't squeeze it roughly in retaliation.

It did however, put more evidence about what he had begun to realize.

            "Really, brother, if you wanted to be mistreated and fucked, you didn't need to go to these lengths... Or were you trying to keep me angry in bed until I could get out of it? It was foolish of you to think that I couldn't fuck you like this just because I'm bedridden."

            "I'm... I'm, sorry, Boss."

            Sans did seem sorry, more guilty at being transparent in his desire more than anything.

            "It's too late for apologies. Strip. Now."

            Sans swallowed, before lifting his sweater over his head and tossing it carelessly to the side. Papyrus watched his movements, studying his brother's bones and marks with a critical eye. The wax was still wet in some places, already drying in others. It continued to make him look wounded... he liked the look on Sans. They’d both experimented with knife play here and there on some occasions before, but Papyrus had never found a real appeal or fascination beyond running it over his brother’s bones or nicking him slightly. Considering his brother’s lesser HP, this new safer kink may very well become something common between them.

            Feeling Sans squeeze his femur again reminded Papyrus of his discovery, and he decided if Sans wanted to pay attention to his wound that bad he would need to pay the full price for it.

            "I have you all figured out now, brother."

            "B-bro? Ack, oh, hmn??"

            He moved Sans so he could strip himself, and reached down to his bandaged leg and tore the wrappings from his bones. Sans made a distressed noise at the crack in his femur, like the first time he'd seen it, but Papyrus wasn't about to let him panic over it again.

            He spun Sans, mindful of the candle in his hand, until he was straddling over Papyrus' lower ribs on his hands and knees, pushing his head down to the crack in the bone.

            "You like my injuries. You like seeing these wounds your powerful brother carries and bare without complaint, don't you? Well if you want to see it that much, I want you to worship it. Lick it like you would my cock."

            "Being laid up hasn't made your limbo go down, I see."

            Sans sounded the part of his smart aleck self, but moved to lick the wound without hesitation, lapping his tongue over it with slow and repetitive strokes. Papyrus took pleasure in the fact that Sans didn’t deny the accusation. It felt good to finally have the puzzle piece clicked into place.

            Though the sensation that came from this was an odd one. Papyrus was by no means ticklish anymore, but the feeling reminded him much of the same sensation... Though perhaps pleasure more like a wet feather ghosting across his bones would be a better description. Putting it in the back of his mind for now, he pushed Sans' shoulders down and by learned instinct, Sans raised his hips in a default movement.

            It made him growl, and all of this was definitely making him hornier. Sans' pelvis was glowing around the bones, but not yet forming an erection or a pussy. It was hard to know if he was intentionally holding back until he knew which one Papyrus wanted, or because he couldn't decide what he wanted on his own.

            "Give me something to stroke, Sans."

            In answer, Sans stuck his tongue into the wound. Unable to stop the flinch that tore through him, hot wax spilled onto Sans' tailbone and then down into his pelvis bones. Sans arched so sharply with such a deep shriek Papyrus was surprised he didn't snap something.

            "P-Papyrus... ahhngn..."

            What a horny brother he had. Even something that must have been very painful turned him on this much. He was drooling and shaking so furiously from the pleasure that Papyrus was gratefully reminded how genuinely happy he was that his brother was such a huge masochist. Otherwise, those moments when he was less than perfect or not cruel intentionally would have been embarrassing. He decided to cover his slip with a command.

            "Give me something to fuck, now."

            Sans obliged, crawling forward at Papyrus' push to raise his hips up. Papyrus didn't need a minute - he was ready to go now and as soon as Sans lined up ahead of him, he grabbed his brother tightly by his lower spine and pulled him down.

            "F-fuck, Papyrus, fuck!"

            Bedroom cursing was the only time Papyrus believed cursing should ever be casually used, and he agreed wholeheartedly with Sans' statement. Sans moved to rest forward on his arms between Papyrus' legs, making his lower half higher than the rest of him and fully impaled.

            Normally, he would have taken the lead now and raised and slammed Sans back down on him, but with hot wax still dripping down his hand and arm, that would be hard to do without flinging wax everywhere - or Asgore forbid - actually burning Sans with the flame and quite possibly setting something on fire.

            Thankfully, Papyrus always had a plan.

            With a grin, he grabbed ahold of Sans' lower spine again and tipped the wax to fall on his tailbone. Sans reacted the way he'd expected, moaning and arching up where Papyrus was eagerly waiting to slam him back down again. They both swore at the feeling in unison, and Papyrus decided then and there despite his preference for fucking Sans any day, this was quickly becoming a new favorite position. Without wait, they both continued to repeat the same movements - both groaning through their teeth.

            "Papyrus - Boss - fuck, whoever, whatever, oh shiiiittt..."

            Sans spread his arms wider apart to hold onto Papyrus' shins instead, alternating from shoving his face into the sheet to scream and moan and throwing his head back to pant and gasp. Every time the wax struck him, he rose just to be shoved back down on waiting cock.

            "M-more, more, mmm-more, please, ple..."

            "Harder? Like this?"

            He twisted Sans spine, throwing his own head back against his pillow at how tightly Sans clutched down on him in response. He knew just how much pain Sans wanted mixed into his pleasure by how strongly he reacted to it. To say his brother was feeling masochistic was an understatement!

            "Pap... Boss... Boss I'm... I'm gonna... Please!"

            "What Sans? What do you want?" Another sharp twist. "You have to say it if you want it." Sans was greedily clinging his hips down to stay impaled even as red hot wax dripped down his most sensitive bones, but Papyrus wasn't having that. He yanked upward, forcing Sans up again and keeping him suspended for a moment with an almost back breaking grip, before slamming him back down.

            Sans' keen traveled from his throat to his very toes and all the way through Papyrus too. It seemed neither of them were going to last the next minute - or few seconds.

            "Sans. Come.  ** _Now._** "

            That last add on was all Sans needed. Feeling him swell and tighten and the tremors course through his bones was enough for Papyrus to join him. Together, locked tight, they rode the sensations out together, both clutching desperately to stay grounded as they soared. Papyrus could only vaguely be prideful of the colorful exclamations flying from his brother’s mouth, because the rest of him was entirely too focused on enjoying every other part of Sans and how tightly clamped around his cock he was.

            Papyrus came back to his senses first, blowing out the candle and dropping it onto the tray now laden with cold food as he massaged Sans’ spine as he waited for Sans’ orgasm to tamper off too. He was loathe to escape Sans’ tight heat, but knew his brother would stubbornly try to stay impaled for as long as possible if left to his own devices.

            After shifting and groans on both of their parts and a minute later, Papyrus had Sans turned the right way again and collapsed on his chest, head pressed under his jaw. His brother was normally very talkative after sex for a few minutes, or dead tired - normally instantly drifting off.

This time around proved to be the latter, as he could feel Sans already sinking into sleep.

            "Hey, stay awake. You have to get cleaned up. You can't sleep in bed covered in wax like this. It's filthy."

            "...can't make it to... the bathroom. Sorry."

            "Nh."

            He couldn't really force Sans to go in this state, and even if he could, he didn't truly want to. Sans was likely to fall asleep halfway in the tub and flood the house if he somehow didn't injure himself.

            But still. There needed to be boundaries. Right now the wax mess was contained to Sans near entirely, and it  **HAD**  to stay that way.

            "You mustn't roll in your sleep. Understand?"

            "...mn-hmm..."

            Sans was already drifting off. With a huff, he reached down and pulled the blanket over them. The wax was probably dry enough it wouldn't come off onto the blanket - though he would be sure to wash everything just in case…Still, he wrapped his arm around Sans to prevent him from rolling, especially off the bed. Last thing they needed was for both of them to be bedridden.

            There was no way they could be trusted to rest together in a bed for any period of time.

**Notes for the Chapter:**

> Leaving a kudos or a kind comment is great encouragement, so thank you for anyone who does! It's really great motivation!


	2. Swapfell; Sans And Papyrus' Pool Table Quicke

**Notes for the Chapter:**

> This fic was inspired by xladymalice's Headcanon Game - A to Z (NSFW) (Quicke & Yearning)

****

                Really, his mutt was absurd. There were at least three dogs playing poker in here right now, and here the bastard was, shamelessly grinding against the small of his back without a care in the world. Sans was trying to keep a straight face as he sipped his drink at the bar, bordering between the anger and the displeasure that came to him when Papyrus gave him these obvious signs of wanting to do a quickie.

                _Horny mutt._

                Muffet had just gone into the back to make food, and Sans was certain – for whatever reason – the mutt had seen this as some sort of sign to be disgusting. Though, all things considered, it was a rather mild, slow, and suggestive grind against his tail bone. Sitting on the stool put the spot of contact just higher than normal, but it was too close to his sensitive lower back bones not to send certain tingles across his body.

                _Fuck_ , he was getting in the mood from it…

                The fact he hadn’t done more than hiss quietly seemed to encourage Papyrus to press a little firmer against him now. Going more from a mere horny suggestion to an attention seeking nudge. Sans knew he needed to make up his mind, quickly.

                The sudden howl at the table behind them reminded Sans they weren’t alone, slightly spooking him and making him sit up straight – when had he started slouching backward against Pap? – and rigidly glare over his shoulder at the dogs.

                Whatever had happened at the table seemed to be causing two of the dogs to holler in laughter while another snarled at his cards. He glanced up at Papyrus, who the shameless exhibitionist that he was, hadn’t been bothered by the sudden noise of the dogs, or distracted. Papyrus looked positively aroused by the situation, more so now that Sans was looking at him in distaste.

                _Fuck this._

He purposefully scooted forward slightly as he hissed, “Not while the dogs are here.”

                In hindsight, _in hindsight,_ even as the words left his mouth and he turned to take a drink, Sans realized… that probably _wasn’t_ the best way to have worded his reply. Not only did it suggest he was willing to fool around here, even right now… It more importantly left off an unsubtle but unintentional hint.

                Papyrus bent down to his cheekbone, a slightly hot and heady pant to his words. Much like he’d expected, the bastard saw his words as a suggestion. Or, by the sounds of it, an order.

                “Yes, M’lord.”

                Sans felt Papyrus lean away from him a slow moment later, and then disappear. The sensation of Papyrus vanishing always felt strange, be it teleporting with his brother or just being in close proximity to him. Sans rested his chin on his upturned hand with a hissing sigh, and glanced at his drink.

                The thing about Papyrus was… He knew his brother better than anyone, and as such he knew he was about to do something that would definitely end up getting this place cleared out… but he didn’t know _what_ his damn mutt was about to do. As easy and predictable as it was to know how things would end up, to see the end of the ride, it was _ride_ itself that often left Sans further believing his brother was unstably unpredictable.

                _Well, I can’t deny that its… bemusing, at least._

Sans suddenly tightened his hand along his drink as a realization set in.

                _Unless it damn well causes me more paperwork…_

Sitting up straight, he started sipping his drink, refusing to rush, just as he heard the sound of an explosion somewhere just outside of Snowdin. The dogs suddenly clattered to and from the table, hurrying to get their bearings – and then mobilized out the door.

                _That fucking mutt…_

He _should_ have just said they should go back to the house. But then again, if he didn’t show up out there, the paperwork might go to the dogs… Or he could probably push it off onto them…

 _Maybe, but they’re so poorly literate_ …

                He felt the air ripple, that strange sensation of subtle heat, and a slight shadow as Papyrus was at his back again. The grinding started up again, this time with Papyrus putting his hands along the bar on both sides of Sans.

                _Don’t rush me._

“I haven’t finished my drink yet.”

                It was revenge, this forced delay, because he knew well enough he was going to have to report the incident to Alphys no matter what. Papyrus only chuckled as he watched him sip deliberately slowly at his drink, likely getting off on that dominant oral fetish trait of his.

                The ministrations against the small of his back felt good. Papyrus was purposefully grinding there instead of against his tail bone, knowing just how sensitive those bones were. The friction and heat grating against him felt good, and he could feel Papyrus swelling behind him.

                Still, Sans had a change of scenery in mind and purposefully turned to the side as he set his drink down. Reaching up to grab his mutt by his collar, he tugged him down to his mouth to kiss, but pulled him back only seconds into it as Papyrus was sucking on his tongue.

                “This better be quick, Papyrus. There are better things do to.”

                His break was almost over, and he refused to be late for his training with Alphys.

                Papyrus started to move him to straddle his hips on the stool, but this wasn’t the change he had in mind. He slid down the stool and gave his brother’s collar a harsh tug, before rising up to caress and slightly scratch his cheekbone with his claws before heading over to the pool table.

                As he glanced over the balls, he couldn’t help but smirk lightly. He and Alphys had played a round – or ten – yesterday, and no one had dared to bother the table since, not until they could finish their last game and declare a winner.

                Though, this game was a lot more interesting than that one, as was the rivalry.

                “Like this, Sans?”

                Papyrus’ voice was husky as he moved behind him and unzipped his pants. Sans contemplated lying on the table before deciding that as much as loved one game over the other, he didn’t want to sacrifice one game _for_ the other. Bracing his hands at the end of the table, he glanced back at his brother as he reminded to warn Papyrus, “Hurry this along. If someone walks in on us, I’m going to be very angry with you.”

                The challenge made Papyrus’ eyes hungry and his tongue curl, and his brother reached around to unbuckle his belt and pull his shorts down. He was about to tell his mutt he didn’t need preparing, but Papyrus was ahead of him and reached around to rub at his clitoris for a few moments, gentle pinching pressure with a slight sting, before grabbing his ecto flesh and spreading him with his fingers.

                A nudge and press later, and Sans felt Papyrus sliding inside of him. Wincing not from pain but from annoyance at the angle because of their different heights, he stepped onto his brother’s boots and stood on his toes to make it easier for Papyrus to thrust inside of him without pulling out. Papyrus chuckled slightly at this, and Sans felt his face burn from an angry embarrassment.

                “What are you laughing at, bastard?”

                “Nothing, my lord~ You’re so cute…”

                He could only hiss in reply as Papyrus hips bucked into his pelvis, spreading him further, and he had to clench a little of everything to keep his arms firm on the table. He kept an annoyed expression on his face, glaring over his shoulder at Papyrus as his panting brother’s tongue waved out from his mouth. He really looked like nothing but a mindless, heat-struck, beast.

                “…you horny bastard.”

                Sans felt a hand descend on his lower spine, squeezing pressure followed by firm strokes, and nimble fingers that knew exactly where his weak spots were. Papyrus was going for broke, and all those sensitive areas were causing Sans to squeeze down tight as Papyrus jerked him back with an attentive hand on his pelvis, rubbing his folds. The thrusts were so forceful that they knocked Sans’ jacket down from his shoulders, and the new tightness made Papyrus gasp his name like a revenant prayer.

                “Saaans, ah, heh, nyeh,”

                “H-hurry up!”

                The hand on his hip moved lower, roved over his folds faster, smushing them down on his clitoris as Papyrus rubbed his spine. It was impossible not to arch at the double assault, and Sans tried to step on the outside of Papyrus’ legs as he felt his bastardly mutt swell, but Papyrus kept him on the inside of his shoes by locking his legs.

                “You love, you love it M’lord~”

                Sans could feel the heat rising from his pelvis along throughout his bones, and knew the moment he orgasmed would be the last straw Papyrus needed to go ahead. With all the heat and thrusting into him, all the restricted movements between Pap’s legs and having to keep his arms ramrod straight, and hearing Papyrus panting so loudly as he called his name, Sans felt his climax rushing him. What his voice lacked in anger made up for in passion.

                “ _S-shut up!!!_ ”

                He locked down on Papyrus, felt his brother gasp his name as much as he heard it, and that thrust sent him over. It hit him harder than he was expecting from a quick fuck, and Sans struggled to – _refused_ to – let his arms give or his face betray his pleasure as he shook and climaxed over Papyrus’ shaft as he trembled head to toe.

                His brother didn’t move but stayed buried deeply in him, continuing to rub his spine and folds throughout both their orgasms until they abated, and then lingering on until Sans had to reach down and stop him.

                Lightheaded, he took a few moments to try and shake off the unexpectedly powerful orgasm before he glared at the front door and seethed, “Don’t think this is going to make up for whatever paperwork you gave me out-”

                He was surprised into silence when Papyrus didn’t pull out of him but pulled him closer from behind and started to kiss his shoulders. He almost snapped this was a _quickie, Papyrus, don’t forget that!_ but Papyrus’ motions weren’t fast or hungry, but slow and pleasing instead. Even the scrape of his teeth were light against his bones.

                He wasn’t sure if Papyrus was just enjoying the afterglow from his orgasm, or if Papyrus was feeling uncommonly sentimental from – by their standards – a rushed fuck that meant little, but the unexpected affection moved Sans in ways he wouldn’t admit. Only half as annoyed as he pretended to look, he glanced at the front door.

                _We still have… a few minutes until those hounds think to come get me..._

Then his eyes strayed to the back door where Muffet had disappeared only minutes ago.

                _Make that one good minute._

He felt his frustration rise. This is why quickies pissed him off, as they didn’t leave enough time for the sex itself, or the afterglow…

                _Still…_

He raised one of his hands to cradle the side of his mutt’s face as the kissing ministrations continued.

                _That’s at least a_ few _more seconds of this, and it seems… we both want to use them._

 

 

**Notes for the Chapter:**

> For anyone who leaves drops a kudos or leaves a comment, it's really appreciated! It lets me know that you guys want more.


	3. Underfell; A Day Forgotten To Remember

**Summary for the Chapter:**

> Sans chooses the wrong day to go Chillby's, and is left conflicted and crushed in the aftermath of what happens.

**Notes for the Chapter:**

> T^T I finally have my old writing software back. Now I can go back and edit and revise the first two chapters! Yay!
> 
> This ended up being an Underfell Sansby, with non-con to dubious consent.

 

           Sans knew exactly how much spiked mustard he could drink before he went from a pleasant buzz to tipsy, to drunk, to intoxicated, and at one time in his life he’d much rather forget about – shitfaced. So he knew himself well when it came to his limits, and more importantly, the Boss’ limits on his drinking.

            Pap already didn’t like it when he went to Chillby’s to shirk work or rewind after a stressful day of dealing with his existential crisises, so he’d been doing his best to at least cut his visits back half an hour.

            That all being said, when Sans felt himself slide from pleasantly buzzed to questionably tipsy, he made sure to nurse his bottle with more care. Boss wouldn’t be more than simply annoyed if he came home in a state of drunkenness – as long as that drunkenness was manageable and Sans wasn’t likely to stumble, fall, or slur his words noticeably. He’d even be less angry about it if Sans kept his puns in line.

            Because one thing Boss hated was a drunken and puns fueled Sans stumbling and slurring around the house. And things between them had been good lately, hell, they’d even been rather great. They were getting along, having sex frequently – his nightmares even seemed to be on the back burner this month, and so he’d been sleeping well. It probably had something to do with being made exhausted before bed, but that definitely wasn’t a complaint on his part.

            So with these things in mind, when Sans felt his thoughts begin to get sluggish and slow only half way through his drink he sat it down and leaned back from it, as if that might help him lean away from the hazy feeling swimming in his bones. He decided to do the old ‘smarts test’ on himself to gauge his drunkenness.

            Pulling out his small scratchpad full of tons of scribbled phallic images in Boss’ honor and some new horrible puns he’d come up to tell that old lady behind the door, he flipped to a clean page and pulled out his old chewed up pen and asked himself one of the hundred or so ‘smarts test’ equations he’d memorized to stave off his depression.

            A particle in free space in one dimension is initially in a wave packet described by…

            He tapped his pen for several moments, blinking at his sloppy handwriting as he read the question twice to process it. Not a good sign, on his part. His motions were slow as he went to answer the equation.

            ψ(x) =

                His mind was drawing a blank, which was really odd, considering he often asked himself quantum physic questions these days more so by habit than desire to continue on from his past interests. The fact that he couldn’t solve a question he’d memorized, or even solve it now, had him frowning and resting his skull against his hand.

            _There’s no way I’ve had that much to drink yet…_

His skull felt warmer to the touch than usual. Chillby came out from the back to bring someone an order of fries, and Sans flipped the small scratchpad back to one of pages full of phallic gloriousness – something everyone would expect of him – as the barkeep went past.

            His eye lights were heavy and his vision was blurring the images badly, but seeing the images scribbled in bright red made him very oddly uncomfortable suddenly. He closed the scratchpad and tucked it away in his pocket again.

            _Gods, my skull feels so heavy._

It was definitely time to head home. As he was starting to get up, hands grabbed his shoulders from behind. Despite his natural spite and the anxiety it caused him when anyone but Pap touched him, his reflex to shrug off or shove someone away felt delayed, and he didn’t manage to do more than slouch away from whoever had a hold of him. Not that it did any good, the hands stayed firmly on his shoulders and followed the motion.

            “Sans, you’ll fall off your stool like that.”

            Normally, Chillby’s chuckle was somehow both acutely unsettling and yet relaxing because it was so deep and crackled like a warm flame, but now it set his bones on edge. He could feel himself tense further as his mind tried to catch up with the feelings of distrust rising in his ribcage.

            “Chillby… You know I don’t like to be touched.”

            Why did the words take so much strength to get out, and yet still wobble? The hands on his shoulders started massaging him, and while Chillby’s heat _should_ have warmed his bones...they made him shiver instead.

            “That’s not how you used to feel about my touch…”

            _This_ again?

            “That was a long… A long time ago Chillbs…”

            “Not that long.”

            His bones were beginning to chatter under his clothes. Yeah, okay, he’d and Chillby had frickle frackled the fuck out of each other at one time, back when he and the Boss hadn’t yet mended their relationship and especially before he’d gotten together with Paps… But he and Chillbs had even left on good terms and they'd rarely ever spoken of it again besides suggestive one-liners from the flame atronach from time to time. Chills had never been forward like this since that time, especially when Sans had made it clear that he solely Papyrus' now.

            Shoving him back with his elbow, he turned on his stool to tell him exactly where to cool it before things got out of hand, but found himself flailing and struggling not to fall from the stood as his balance left him. Chillby pushed him up straight again, spine against the bar.

            Finally, his mind could catch up to what his bones had already been telling him.

            “The fuck did you do, Chillbs…”

            Dragging a thumb down the side of his cheek, the bartender chuckled lowly.

             “Only what you wanted me to do back then.”

            “The hell does that…”

            He was yanked from the stool before he could finish his sentence, discovering to his own horror that his legs wouldn’t support him easily. A rising warmth was now racing upward and outward from his pelvis, and it had nothing to do with how close one of Chillby’s hands suddenly were to those bones.

            “The fuck, Chills, you _drugged me_? The Boss will kill you this if he finds out, you know this!”

            As much as he liked Chillby’s company and even their banter, he fuckin’ loved Paps. Loved him enough that even if Paps was fine with him sleeping with someone else that he’d refuse to on principle. He struggled to pull away from Chillby’s grip, trying to eye the usual crowd around him. If any of the dogs were in here and saw, they’d put a stop to this, but they’d also likely open their traps about it to Boss, since he was in command of Snowdin.

            “He would try, wouldn’t he? But the _danger_ makes things more exciting, anyway.”

            Somehow, that sounded awfully familiar… But he couldn’t recall from where. Chillby’s hand had started to stroke his lower spine, and Sans was finding it hard to think in sentences let alone resist as Chillby easily and silently moved him around the two sleeping patrons at the bar and toward the back door.

            His eye lights sought out the dogs, both wanting and not wanting them to notice what was going on, but they were too absorbed in their card game to pay any attention. As Chillby shuffled him toward the back he clenched his teeth shut instead of call out for them. If he called, this whole thing would surely get back to Paps – but if he handled this himself, he could still sweep this whole thing under the rug.

            Chillby manhandled him from the kitchen outside behind his bar and around the trees behind it. He didn’t try to dilute himself about what Chillby had in mind. He had to make his intentions clear about this while he still could. Already the trees looked like they were trembling around him.

            “Stop, Chillby.”

            “This _should_ be far enough.”

            A sudden push sent him tumbling forward into the snow. With a growl, he turned over as Chillby bent down over him.

            “I’m warning you, knock it off. I’ll forget about this whole thing if you back the fuck off now.”

            With sudden speed his dulled reflexes couldn’t keep up with, Chillby pinned his hands above his head.

            “ _You_ knock it off, Sans. I’m only doing what you wanted me to do. This is what _you_ wanted from me. Why else would you show up here, now, when all week you haven’t?”

            “The hell are you talking about!? Let-”

            His voice was cut off sharply as Chillby unceremoniously grabbed him through his shorts and started aggressively rubbing his pelvis with his hand. It shouldn’t have made him tremble as hard as he did or react as severely, but warmth flooded through his bones like a gunshot. It took him several seconds to be able to calm down before he could form coherent thoughts and words again.

            “What- what the fuck…?”

            “ Aphrodisiacs. A special kind, though. They don’t really kick in unless the person is already feeling aroused. They just make you somewhat sluggish otherwise. Your spiked mustard didn’t seem to really make a difference on its effect.”

            He tried to yank his grip from Chillby’s hands, but the flame monster’s grip on his wrists were relentless. In a lot of ways, Chillby’s strength was a lot like Paps.

            Too late he realized he shouldn’t have thought about his brother. The drugs, the touching, his sensitive bones – he could feel himself forming a vag even though he tried to resist. At this rate, Chillby really was going to screw him if he didn’t stop him.

            The only thing he could think to do was summon a Gaster Blaster to knock Chillby off, but no one alive today knew he had that power and he wanted to keep it that way. Besides, he doubted he’d be able to have it fire without hitting him too… and while he could take strikes, bruises, and even cracked bones, if the blast accidently hit his soul he’d turn to dust.

            It wasn’t worth the risk.

            Which left haggling, which he was _normally_ good at. Negotiation was a strategy he’d been forced to gain quickly back when he’d been the sole provider for himself and Paps.

            _Normally_ he could think straight under duress and speak without slurring or moaning, though.

            “Chillbs, k-knock it off. I don’t- You _really_ won’t like the con- con- sequences of what’ll… What’ll…”

            Gods, it was so hard to think when Chillby wouldn’t stop rubbing and pressing his hand and fingers like that – _I’m wet, I’m wet, son of a bitch, I’m –_ and through conditioning, struggling when he was in pleasure only made it better for him. He tried to stop moving, stop resisting, to stave off what he knew was approaching.

            “Sans, Sans, Sans… This charade turns you on, doesn’t it? Good. I like that too. But soon once the pleasure hits, it’ll be like being in heat. You always felt so amazing when those hit… The few times I ever touched someone and thought they felt ‘hot’ was when I was in you. I couldn’t quite believe it when you strolled into my bar today of all todays…”

            What was so special about today? He’d just come in for a visit at the end of the damn week. He struggled to grasp the date and grapple with any meaning behind it, but his thoughts were too hazy to concentrate.

            “I couldn’t give you this when you were in my sheets back then, not since neither of us knew your brother was coming to Snowdin and our relationship was coming to an end… But I’m happy to see that you still want this. But, don’t worry…”

            Chillby grabbed at his shorts and pulled them down. As much as he’d tried to calm himself, the glowing red vagina leaking in his pelvis was a stark contrast. Seeing it himself made his cheekbones burn. Leaning over him and sticking his fingers inside, Chillby purred, “…Papyrus doesn’t have to know a thing.”

            The shock of being penetrated with something so warm and hot while he laid in the snow was too much for his control in this state. With only a few forceful thrusts, Sans was clenching and trembling, struggling to resist shouting as his body came without consent.

            “Da- Damnit, Chi-Chillby I’ll…. I’ll..! I……?”

            Confusion filled him as steadily as a rising heat spreading throughout the marrow in his bones. Instead of the pleasure dying down after his orgasm, it continued to rise throughout his limbs – he felt hot, as hot as Chillby’s fingers.

            “There’s that expression.”

            Chillby’s hand moved to thumb at the drool coming from his mouth, chuckling as his fingers continued to fuck him.

            “The one that gets easily lost in pleasure… I missed that.”

            Sans didn’t seem to notice his wrists weren’t being held down above his head any longer. He was too focused on the fingers that kept ramming inside of him… of the mouth that went down on him. Gods, it was hot – it burnt – but that tip between pain and pleasure turned him on the most, and Chillby knew him well enough to know that. His legs were still weak from orgasm and he couldn’t even resist as they were parted and raised over the bartender’s shoulders, his shorts discarded into the snow.

            _Shit, shit, shit, shit_ – he had to stop swearing, that only turned him on more. But it was so hard to focus on anything. His thoughts were going from a muddled and jumbled mess into a murky haze that couldn’t be penetrated.

            _Oh god don’t think about penetration!_

He gasped as heat singed his clit. It hurt enough that he lifted onto his arms, struggling to remember what he could do in this situation, but another flick had him falling back and slapping his hands over his mouth. Not just to muffle a scream, but the panting that came with being so aroused. 

            _It really is like being in a damn heat! I can’t get my head to clear at all!_

He was already about to come again, and it filled him a genuine fear. If he was already having this much trouble focusing, if he came again he’d completely lose his damn mind to pleasure.

            But it was harder said than done, as pushing or trying to crawl backward didn’t accomplish anything. He tried to summon a bone construct – to do what at this point he wasn’t even sure – but couldn’t call or focus his magic at all. All that calling on his magic managed to do was make him convulse into shudders as it called his vag to his attention.

            Chillby rose over him again, shoving three fingers into him that burnt – burnt – burnt – and that was all it took before Sans knew he was about to come.

            _No, I can’t…_

The feeling inside him began to blister into pleasure.

            _I can’t, I can’t I- I- I Pap’s be- so-_

_**PAPS**_

From his toe bones to the crown of his head, heat surged throughout him so strongly that he imagined he was actually on fire. The feeling wouldn’t stop – it kept increasing, even after Chillby withdrew his fingers and Sans curled up on his side, knowing he was definitely going to convulse so hard that his bones broke apart – he was going to break into dust – the forest would catch fire around him – everything would burn and mix with his dust-

            “NnNGh… AHHch…”

            He couldn’t think anything anymore. When Chillby shrugged off his hoodie and unzipped his pants, Sans couldn’t focus on anything besides what was between his legs. It made him throb. It made him  _burn._

            Hands moved him onto his knees, yanking his sweater up so his ribs would press into the snow. He came again at the feeling – steam was certainly exploding from the contact – and felt something probe at his folds from behind.

            “You want this, don’t you Sans? Say it. Say ‘fuck me.’”

            The thing kept probing at him, why wasn’t it going inside? He pressed his chest further down into the snow and clung to the whiteness under him, raising his hips further. Why didn’t it go inside? He wanted it – he wanted it inside. He was so hot, he burnt everywhere – inside, inside please – and his legs were about to give out and he couldn’t see – and it wasn’t inside---

            “NNGNNN.”

            Finally, finally, it was inside – so hot, so hot, so hot but not as hot as him – he was scratching at the snow, clawing at it, digging his way through it.

            Thrusting, ramming, bones clacking, the sounds were everywhere. Desperate panting and harsh breathing, two voices hissing, and Sans could feel it – feel his desire completely take over. It made him light-headed. Did he even have a skull anymore?

            Things were going dark, going hazy… He could still feel everything, every motion and every burst of heat that engulfed him, but he couldn’t think anymore.

            His mind went blank.

 

…xXx…

 

            He wasn’t really sure how long it was before his thoughts started trickling back in again. They were slow and dulled. He hadn’t lost consciousness, he was sure of it, but he’d lost all awareness of himself at some point.

            A noise caught his attention, and he turned his cheek from the snow to see Chillby’s back as he shrugged on his coat. Memories trickled back.

            Being fucked in the snow on his hands and knees like a mutt, wordless and breathless – to being pushed up against a tree with his arms behind his back, gasping encouragements to be fucked – to being in his lap, taking it deep in his back as they’d both stroked his front. Chillby still kissed like fire, and his tongue had been as warm as he had remembered. Sans hadn’t been able to stop slurping at it, had stopped trying to quiet his moan. But he couldn’t remember any of the mindless things he’d begged and moaned in ecstasy. It was too much of an intoxicated blur.  

            A figure moved over him, pulling him into a sitting position to push his arms into his coat. He’d been dressed at some point. He felt so weak, so fucked, and yet… Still so horny. Only now that he wasn’t caught in the moment could he find some semblance of sanity again.

            “That lasted longer than I was expecting. But it felt too good to want to stop so soon. Especially when you gave up pretenses like that.”

            Sans could already feel the sins crawling on his back. Drugs or not, he hated himself for his lost of control. Even now, he still wanted more, wanted to be fucked again until he passed out and forgot everything. It pissed him off, these damn drugs, and his own damn weakness. It made his words and voice, though hoarse, biting. 

            “You don’t fuck as good as my brother does. You never have.”

            Chillby’s expression went dark, and Sans was hoping Chillby would hit him. Someone ought to. But after a few moments, his flames returned to normal and he knelt to haul Sans to his feet again, holding onto his upper arms to keep him from falling over.

            “Maybe not… But you’re a much better fuck than you used to be… If you fuck that brother of yours like that, it’s no wonder he’s so possessive over you. When you submit so willingly and enthusiastically like that… Makes a monster feel powerful, like a god.”

            A few clumsy uncertain steps later, and Chillby had him resting against the wall by the back door. He watched as Chillby opened the door and popped his head into the kitchen.

            “Been gone longer than I would have liked… Hope I still have a bar to go back to in there. You can rest upstairs in the bedroom before you go home.”

            He felt so weak. Weak in mind, weak in body... Weak in control. He rubbed his legs together, trying to dispel whatever he could down below, but it didn’t seem to be helping at all.

            Chillby disappeared into the kitchen and Sans found himself pressing his hands into his skull and digging his hands down his cheeks.

            “Fuck!”

            _What the fuck was Chillby thinking doing all of this…?_

He heard Chillby swear in the kitchen, then call back, “Your brother just came in. Go upstairs and clean up. I’ll tell him you left a while ago.”

            The back door closed and Sans clutched at his arms, feeling sick enough to lose the mustard he’d ingested earlier… Maybe that’s what he should do… Spit it all back up to get it out of his system. Fucking had cleared a lot of it from his body, but he could still feel fluid pooling in his shorts that kept trying to drip down his femurs.

            _Boss… Boss can’t know… I have to… I have to get home before he does. No one can know…_

He didn’t trust himself to teleport. He could only keep his knees together, and his coat pulled tight over him as he made his way out from behind Chillby’s, desperate to get to home before his brother and Chillby got done talking.

            _Maybe he could clean up… There might be time…_

His vision swimming, still reeking of sex and dripping, still hot, he did his best to keep taking a step forward as he scanned the area for monsters.

            Paps couldn’t know. His brother would kill Chillby… He’d never forgive Sans for what he’d just done. Their peaceful relationship would be broken. _Paps wouldn’t trust him anymore._

             He could _never_ know.

           

**Notes for the Chapter:**

> Poor Sans, he's so confused and distressed... I might leave this as a one-shot unless you guys might like this one to have a follow-up chapter. This one is up to you.


	4. Swapfell; The Nightmare Lotus

**Notes for the Chapter:**

> This fic was inspired because of xladymalice's Headcanon Game - A to Z (NSFW) (Aftercare & Favorite Position)

 

                Papyrus had a nightmare. Sans knew that before he even registered what was going on. The scent of flavored smoke in the air had stirred him from his sleep. He rubbed at his eye sockets before glancing over his shoulder. Papyrus was sitting up on his side of the bed, head hung low with one hand against his temple as the other held onto a smoke clutched between his fingers. He was quietly expelling a gust of smoke down on the covers covering his lap.

                His brother’s gaze was… distant. Dismal, even, as if he were staring into an abyss. He didn’t even seem to notice as Sans shifted the covers away as he sat up, and moved to sit against his side.

                “Papyrus.”

                Still no acknowledgement. Sighing softly, Sans wondered if it was okay to touch his brother just yet. He couldn’t help but remember the time Papyrus had near strangled him in a stupor once before – lost in whatever had upset him so bad and made him so furious – before coming to his senses. It had only happened once before, but… It was enough to give him pause for a few moments more.

                He waited until his brother took another drag of his smoke before reaching out to wrap an arm around his back to grab his shoulder, and rest his other hand on the shoulder nearest to him. His brother didn’t so much as flinch, more like slightly turn his head to the side.

                “Papyrus.”

                Still no answer, but his brother moved to rest his free hand over Sans’. His gaze was still down on the covers, still so distant. Sans was glad to see his brother wasn’t in a delusion from the nightmare – just not all here yet. He cupped his brother’s face, dragging his hand up his throat to his cheekbone before turning Papyrus to look at him.

                “Who am I, Papyrus…?”

                His brother stared at him for several moments before reaching up to touch his throat. His hand slid to the back of his neck and began to expect each bone slowly. His hand was trembling.

                “M’lord.”

                _Oh._

Papyrus wouldn’t be talking about it, then. It was something he’d found out about his brother – if he called him Sans, he could be enticed to speak about his nightmare with enough time to settle his mind. But like this, he knew it was Papyrus’ way of saying he didn’t want to talk about it – he didn’t want to think. Sans knew some things that went on in someone’s mind just needed to be respected in silence.

                He grabbed his brother’s jaw, dropping his expression into one of mild annoyance and distaste. His grip seemed to draw Papyrus a little further out of his thoughts.

                “That’s right. Now get up and get dressed, Mutt.”

                The order seemed to be what he needed, as he turned away after running his fingers down Sans’ spine. Sans watched him get up and head over to get dressed for a few seconds before he moved to stand up. The room was full of silence besides the shuffling of clothing, the scent of smoke wafting through the air, and the steps across the floor.

                _It’s not enough._

“Today I have a lot of important assignments in the Capital.”

                His voice was sharp and cutting through the still air, as he wanted it to be. He grabbed Papyrus’ boots and chucked them so they _thumped_ against the floor as he sat on the bed and pulled his leggings on. His brother bent, picked them up, and sat on the bed as he pulled them on.

                Pulling his gloves on, Sans hissed as he stated, “It might take all day. Why does the Capital always have to be such a mess?”

                He was fastening his bow on when he saw how Papyrus’ gaze still wasn’t focusing on him, not even when he was purposefully showing off the angles he knew he liked best. It made Sans grit his teeth, before he made himself relax. He turned and crawled back onto the bed, and sat on his knees.

                The movement caught his brother’s attention and he turned to regard him, expression still far darker than Sans liked. He trailed his finger invitingly before he stopped and instead pointed before him.

                “Come here, dog.”

                Papyrus didn’t need to be told twice. He moved across the bed to kneel on his knees before him. Sans judged his brother for several seconds before he reached down and undid Papyrus’ belt. The slow movements brought Papyrus’ hands up – not to stop him – but to reach toward his neck again.

                Catching them, he pushed them down on either side of Papyrus as he commanded, “You _will_ keep them here… and you will give me all of your attention.”

                His voice did wonders on Papyrus. Already his gaze was sharpening, coming into focus, and he was already forming below. Sans wasn’t really in the mood for this, but as he grabbed the sides of his brother’s hood and brought him in for a kiss and felt Papyrus reciprocate, he knew he could be.

                Papyrus’ tongue twirled and wrapped around his, but he kept to his own mouth, wanting Sans to deepen the kiss and suck on his tongue. Sans obliged him, letting Papyrus suck him as he pulled Papyrus closer. The feeling in his mouth and bones was hot, and spreading down into his pelvis. He grinded softly down on Papyrus’ cock, feeling Papyrus jerk slightly with the compulsion to thrust up inside of him but knowing better – knowing it was better to wait.

                He continued with his ministrations for several moments before he shifted to straddle Papyrus – or more accurately pulled Papyrus so he slid underneath him. Sans didn’t need his hands to line them up as he slid his lubricated pussy down on Papyrus slowly, stopping halfway in as he controlled just how much depth was and was not allowed.

                Sans could feel tremors racing up his brother’s arm, where his mutt battled the desire to seize him and impale him. That was the sort of vibrant reaction he was searching for and he slowly bobbled up and down where he was, in no rush to go any further.

                “Look at me.”

                “S-S-“

                He cut his brother off with a kiss. He shifted his hips further, slid down further, felt his brother’s legs quaking underneath him and his hands clench the covers – felt it all and did not look away from Papyrus’ gaze so his brother would do the same.

                And then when Papyrus’ gaze went hazy for an entirely different reason than before, he sunk down on him fully, closed his legs around his brother’s, and clenched on him as tightly as he could.

                “S- _Sans_ -”

                “Just look at me~”

                “ _MMN_ ,”

                “Shhhh~”

                His brother’s choked gasps made him wetter, made him squeeze tighter as he brought Papyrus back into the kiss. He swallowed his moans, all the while making certain Papyrus didn’t look away from him for even a second.

                “I’m right here, Papyrus. I’m right _here_ , with you. I’m right in front of you.”

                He dropped his voice and shivered as Papyrus thrusted inside of him, not able to hold back from doing it even though it had been an unspoken order between them. Sans wasn’t angry though. He took a moment to just enjoy the pleasure before he continued.

                “Your right here with me… _Inside_ of me.”

                Papyrus’ groan turned into a deep vibrating growl that had Sans clutching even tighter and trembling with his brother before it tampered off into a needy groan. Greed and lust covered Papyrus’ face, but his eyes expressed his adoration – undying love – and absolute thirst for everything Sans was offering him.

                “Good boy,” he praised, “good boy… That’s right… Make me, Papyrus. _Make me_.”

                That was all he needed to say, all Papyrus needed to hear. He thrusted into him, fingers digging at the sheets and his whole shuddering frame shaking Sans to pieces as Sans rode his thrusts, meeting them with tightly timed clutches as they both refused to even blink in blasphemy of missing an expression on the other’s face.

                Sans couldn’t take the noises Papyrus was making, the whines, groans, _the growls_ – and not the passionate way Papyrus was hyper-focused on him. He moaned sweetly and longingly as he came, pulling Papyrus closer – pulling him with him as Papyrus reacted to him and came with him, gasping his name like the most committed vow, continuing to move inside him even though it had them both in spasms. Still, they both refused to look away even if their minds wanted to blank.

                The climax’s high lasted for several seconds as they both tried to swallow the other before Sans couldn’t resist and ducked his face slightly – but Papyrus pushed him back up to keep kissing him. Sans let Papyrus greedily capture his tongue, let him delve it deeply into his mouth, before he grabbed the sides of Papyrus’ face and wrestled for control of it, sucking and grazing his teeth against Papyrus.

                Finally, as some of the heat settled, they remembered they needed to separate enough to speak – to breathe. Sans rested his face on his brother’s shoulder, completely spent. Papyrus held him, clutching him close desperately and protectively, pressing his mouth against his skull.

                For a long while, neither of them spoke before Papyrus broke the spell of silence put over them. His voice was slightly raspier than normal.

                “I don’t want to be without you. Never without you… Let’s stay like this.”

                Normally, Sans would get mad at his brother’s suggestion. They had things they had to do, _a reputation to uphold,_ and lazing around made him paranoid and anxious… But he kept recalling the expression Papyrus hadn’t been able to shake off until Sans had made him. He didn’t want it to resurface on his face. He couldn’t prevent it from coming back forever…

                …but he might be able to keep it at bay for now, silence whatever demons and insanity haunted and clung to his brother’s thoughts and dreams.

                “…I’ll call in.”

                Papyrus moved him back, unable to hide the look of surprise on his face. It made Sans curse inwardly wondering if he’d given in too easily – _he should have debated it_ – before he shifted and scowled at his mutt.

                “You better be fucking grateful.”

                The look on the bastard’s face spoke volumes on just how grateful he was to hear those words, and he pulled Sans closer, fingers digging in painfully in gratitude. Sans didn’t stop him.

                He let him.

 

 

**Notes for the Chapter:**

> By-the-by, chapter two is completely different than how it used to be - go back and read what's there if you haven't yet <3


	5. Fanged Glory

**Summary for the Chapter:**

> Set in the Mythtale AU, Swapfell Universe. 
> 
> Sans discovers his servant's hidden fangs, and can't pass up this opportunity.

 

                Sans stood, mystified, and _horribly_ aroused. Papyrus moved his hands down to spread the deliciously tender looking folds to reveal the devilishly laden fangs within. The barbed clit especially seemed to somehow proudly display itself further at his movements.

                Sans had stumbled upon this secret by pure chance; he’d been in an aroused mood after leaving the torture chambers just around the time Papyrus normally fed, and wasn’t it nice that their desires so closely intersected like this? He’d made quick work of moving apart his servant’s robes as soon as they’d gotten into the bedroom. And although he’d been a little unsure why Papyrus had lightly protested, it became abundantly clear now as to why.

                “Are those… fangs?”

                Flushed, his servant said, “I, I normally pull them back in before I move the robe…”

                “Pull them back in?”

                Transfixed, Sans watched as Papyrus’ fangs slowly seemed to sink back into his ecto-flesh – the fangs hardly seeming to be discernable from the rest of his magic. Only now that he’d seen them be pulled inside could he tell there was any indents left behind.

                “Does that hurt?”

                “It tingles, M’lord.”

                “Can you do that in your other flesh?”

                “The fangs?”

                “Yes!”

                “Uh, ye-yes! I can.”

                “Show me, now.”

                Confused but intrigued, Papyrus moved his hand around his flesh, a soft patting motion followed by strokes. The flesh moved and shifted, reshaping into his servants hard and robust cock. Sans watched intently as fangs – larger in size but less in number than the vulva – protruded along his servant’s phallus, and a curved one sprouted from the tip.

                All of a sudden, his servant’s pleasure and incredibly agreeable nature to sounding was made a thousand percent clearer to him.

                “Why did you hide these from me?”

                “I didn’t want to harm you, M’lord…” His features suddenly twisted to worry as he hurriedly said, “D-don’t worry, I can keep the teeth back-”

                “Quiet. I’m trying to decide if I want to ride you or have you ride me…”

                He placed his hands in front of his face, deeply focused on his thoughts.

                “B-but M’lord… Are you certain?”

                He shifted awkwardly on his feet, but his servant didn’t fool him. His body and face may have been expressing concern, but the hunger in his eyes was undeniable. The fact that his lord wasn’t disgusted or horrified by his fangs was making him hard enough to tremble.

                It was that lusty gaze that settled things. He pushed his servant back down against the bed, and moved to straddle him, eyeing the fangs with a trepidation that didn’t come from fear. He felt the fangs with his fingertips, testing their strength and more importantly, their sharpness. If his servant’s breathy pants and twitching was any indication, his fangs were very sensitive to touch. Sans couldn’t stop his hands from exploring, raking his bones along the fangs to lightly scrape them. They were already drawing very shadows trails of blood. The sensations seemed to madden his servant further.

                _Oh? That was quick._

                His magic had already formed in his pants, and a familiar heat and wetness was spreading.

                “Of course I’m certain. You don’t even know how much of a turn on for me this is, do you?”

                He couldn’t keep from blushing at his own words and admission, but he’d trust this with his servant. Papyrus had already found out about his masochistic nature, and they’d explored it together several times already. This was just an upgrade – a chance to make his incredibly durable body experience a new type of agony and pleasure.

                His servant’s hands moved to his hips, and began removing his clothing – donning the role he was so accustomed to now. The both of them were shaky and had yet to do anything substantial as of yet; revealing just how much this had turned them on.

                As Sans lined himself up, he pressed Papyrus down so he laid flat on his back. His servant gazed up at him with vividly glowing eyes.

                “M’lord?”

                Grinning, he said, “Now lay back and behave. That’s an order. Your lord will take care of _everything_ now.”

                Then he slammed himself down.

 

 

**Author's Note:**

> I am @luna-sin-sin on Tumblr, and run a nsfw blog where I post my writing from inspiration I get from Undertale artwork. *Please* don't follow me if you're a minor. 
> 
> Love what I do? Wanna support me make more fanfiction? I now have a Ko-fi page if you'd like to be my patron and donate! And as thanks, I'd be more than happy to write you a fanfiction of your OTP or favorite characters interacting as a thank you, and put it in my Merci series as a gift fic to you <3 
> 
> https://ko-fi.com/lunasi


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